Apparatus for monitoring the rails of a railway or tramway line

ABSTRACT

A laser apparatus for monitoring the rails of a railway or tramway line, characterised by comprising at least two measurement units ( 4, 8 ) mounted on a railway or tramway carriage and operating at least on the inner part of the two rails ( 6 ), along which said carriage is made to advance, and a unit for processing the signals transmitted by said measurement units, each of which comprises at least one triangulation reading device.

[0001] This invention relates to a laser apparatus for monitoring therails of a railway or tramway line.

[0002] The rails of a railway or tramway line are known to undergo wearand deformation with use, these tending to increase with time until theyaffect the entire rolling stock with vibration, noise and abnormalstressing, which progressively increase until the rails have to beground or replaced.

[0003] The correct moment at which such work needs to be carried outdepends on the extent of the deformation, which can be evaluated byperiodic measurements of the rail parameters, using particular contactsensors which however are able to operate only on individual parametersand substantially limit the usability of the measured data.

[0004] A general laser measurement method known as triangulation can beused to measure the profile of objects in general without contact.

[0005] With this method, the object is struck with a laser light beam, avideo camera being used, with its optical axis inclined to the directionof the laser beam, to read the shape generated by the interferencebetween this beam and the object under examination. This method hasfound many applications in various technical sectors, but has never beenapplied to the railway or tramway sector to measure the profile of arail while in movement, and in reality it would seem to be inapplicable,given the specific requirements of this sector and in particular theneed to make the measurement while in movement at high speed, the needto measure all the parameters necessary for complete knowledge of thestate of the railway or tramway line, and basically the need to handleall its data with a single information technology system to enable ananalysis of the correlation between the various data to be achieved. tohandle all its data with a single information technology system toenable an analysis of the correlation between the various data to beachieved.

[0006] DE-A-19510560 discloses a monitor having at least one lightsource emitting a narrow beam to illuminate the contours of the rails tobe inspected and at least one camera continuosly recording and storingimage data from the light beam reflected from the rail. The beam lies ina plane at a defined angle to the vertical plane of the rail but thelight source is displaced or located sideways and upwards relative tothe horizontal contact plane at top of rail surface over an area. Thelight source and the camera are mounted on a measurement head and thecamera is located at a defined angle relative to the vertical plane ofthe rail and the horizontal contact plane.

[0007] An object of the invention is to measure the undulatory wear ofthe rails.

[0008] A further object of the invention is to measure all theparameters of a railway or tramway line without any contact with therails and without having to use mechanical centering devices.

[0009] A particular object of the invention is to acquire informationconcerning the real profile of the rail, its degree of wear and itsvertical and transverse deformation.

[0010] Another object of the invention is to be also able to effectthese measurements at the points end of a rail.

[0011] Another object of the invention is to measure the geometryparameters of the rails, including their difference in height.

[0012] Another object of the invention is to effect all the railmeasurements with the measurement apparatus insensitive to oscillationand deformation of the vehicle on which it is mounted.

[0013] All these and further objects which will be apparent from theensuing description are attained, according to the invention, by a laserapparatus for monitoring the rails of a railway or tramway line, asdescribed in claim 1.

[0014] The invention is described in detail hereinafter with referenceto the accompanying drawings, in which:

[0015]FIGS. 1, 2 and 3 schematically illustrates the principle on whichthe measurement of the profile of a rail is based according to the priorart;

[0016]FIG. 4 schematically illustrates the principle on which themeasurement of the undulatory wear of a rail is based according to theinvention;

[0017]FIG. 5 shows the apparatus of the invention in the embodiment forreading the complete profile of the rails, their undulatory wear and thetrack geometry;

[0018]FIG. 6 schematically illustrates the system for automaticallycompensating the errors due to the elastic deformation of the frame ofthe railway or tramway carriage; and

[0019]FIG. 7 is an external perspective view of a container containing ameasurement unit.

[0020] As can be seen from the figures, the apparatus of the inventionuses the principle of measurement based on optical triangulationobtained with a laser beam and a dot matrix. More specifically, withreference to FIG. 1, the laser beam 2 is generated by a solid statesource 4, for example by a cylindrical lens (not shown) able touniformly distribute the beam 2 and shape it as a lamina.

[0021] The interference between the laminar laser beam 2 and the rail 6displays a line of light related to the rail profile, this latter beingread by a special video camera 8 positioned at a certain angle to thelaser beam 2 and using a high resolution sensor (1000×1000 pixel) andvery high acquisition frequency (100-2000 determinations/second).

[0022] The invention is described in detail hereinafter with referenceto the accompanying drawings, in which:

[0023]FIGS. 1, 2 and 3 schematically illustrates the principle on whichthe measurement of the profile of a rail is based according to the priorart;

[0024]FIG. 4 schematically illustrates the principle on which themeasurement of the undulatory wear of a rail is based according to theinvention;

[0025]FIG. 5 shows the apparatus of the invention in the embodiment forreading the complete profile of the rails, their undulatory wear and thetrack geometry;

[0026]FIG. 6 schematically illustrates the system for automaticallycompensating the errors due to the elastic deformation of the frame ofthe railway or tramway carriage; and

[0027]FIG. 7 is an external perspective view of a container containing ameasurement unit.

[0028] As can be seen from the figures, the apparatus of the inventionuses the principle of measurement based on optical triangulationobtained with a laser beam and a dot matrix. More specifically, withreference to FIG. 1, the laser beam 2 is generated by a solid statesource 4, for example by a cylindrical lens (not shown) able touniformly distribute the beam 2 and shape it as a lamina.

[0029] The interference between the laminar laser beam 2 and the rail 6displays a line of light related to the rail profile, this latter beingread by a special video camera 8 positioned at a certain angle to thelaser beam 2 and using a high resolution sensor (1000×1000 pixel) andvery high acquisition frequency (100-2000 determinations/second).

[0030] The digital signal generated by said video camera 8 andcorresponding to the line of interference of the laser beam 2 with therail 6 is fed to a processor unit which, on the basis of the geometricalparameters of the apparatus, is able to reconstruct the real profile ofthe rail with high precision.

[0031] In its most simple embodiment, shown in FIG. 2, the apparatus ofthe invention comprises two triangulation reading devices, one for eachrail 6, which together form a measurement unit 10 mounted on board arailway carriage, on which the processor unit is also installed.Alternatively, the carriage can be equipped with a recording unit ableto memorize the output signals of the two reading devices for theirsubsequent processing.

[0032] The two triangulation reading devices of the describedmeasurement unit 10 are positioned such that the two laser beams 2emitted by the two sources 4 are focused on the inner side of the tworails 6 and hence display their inner upper bands, i.e. those mostsignificant in determining any deformation and/or wear.

[0033] However, in a more complete embodiment, shown in FIG. 3, witheach rail 6 there is associated a measurement unit comprising threetriangulation reading devices, i.e. three laser sources 14 and threevideo cameras 18, operating on three different longitudinal bands(inner, upper, outer) of each rail 6, to measure at a predeterminedfrequency the complete profile of each rail. This embodiment isparticularly useful at the points end 12 of the rail 6, i.e. itstapering portion located at the rail switching points.

[0034] The real profile of the rail is hence transmitted to theprocessor unit, which compares it with the theoretical profile todetermine the degree of wear of the rail.

[0035] In the schematic embodiment shown in FIG. 4, each measurementunit also comprises a further pair of triangulation reading devicespositioned longitudinally aligned along each rail 6 and focused on thetop of the rail head. In this case the two video cameras 28, which haveread the two light profiles obtained by the interference of the twolaser beams generated by the two sources 24 with the rail 6, feed thecorresponding signals to the processor unit, which using suitablesoftware is able to calculate the derivative of the differentialmeasurement obtained from each of these and hence determine theundulatory wear of the rail.

[0036] In this case the two video cameras 28 read the top of the railprofile, to enable the processor unit to analyze the succession ofprofile parts read with the predetermined frequency and to determinewhether the rail contact surface is rectilinear.

[0037] In the more complete embodiment of the apparatus of theinvention, shown in FIG. 5, on board the railway or tramway carriagethere are installed for each rail 6 three reading devices 18 for thetransverse profile of the rail, which act on three differentlongitudinal bands of the rail, and two longitudinally aligned readingdevices 28 focused on the top of the rail head and forming with thepreceding three a central measurement unit 10. In addition to this,there are provided on the carriage a further two end measurement units,namely a front 20 and a rear 30, preferably positioned at the maximumdistance from the central unit 10 compatible with the longitudinaldimensions of the carriage.

[0038] The front end unit 20 and the rear end unit 30 each comprises,for each rail 6, a triangulation reading device, which with thecorresponding reading device of the central unit 10 is able, with thepredetermined frequency, to read at three longitudinally spaced-apartpoints of each rail the two characteristic coordinates of the point atthat instant, i.e. the vertical coordinate, measured on the top of thehorizontal surface of the rail, and the horizontal coordinate, measuredon the inner vertical wall of the rail head. These two coordinates,which as stated are read at three longitudinally spaced-apart points,enable the processor unit to calculate the various parameters of thetrack geometry, and in particular:

[0039] the gauge,

[0040] the radius of curvature,

[0041] the horizontal alignment,

[0042] the vertical alignment,

[0043] the skew.

[0044]FIG. 6 shows schematically the principle of compensation for theerrors due to elastic deformation of the railway or tramway carriage.With this, the position in height of each triangulation reading devicelocated in the two end measurement units 20 and 30 is monitored by alaser bar 32 emitted by a source 34 positioned in the centralmeasurement unit 10 and received by a sensor 16 positioned in the endmeasurement unit 20, 30 and able to constitute a precise alignment ofthe points of measurement. Lack of alignment results in a signal whichby means of suitable software is able to automatically compensate theresultant measurement errors.

[0045] Each central measurement unit 10 and end measurement unit 20, 30is preferably contained in a strong metal container (see FIG. 7)provided with brackets for its mounting on the frame of the carriage.The bottom of the container 22, facing the rails 6, is provided withwindows 36 for the laser source 4, 14, 24 and for the video cameras 8,18, 28 the windows being able to be simultaneously closed by a slidableprotection screen 26, operated automatically by the system.

[0046] To ensure automatic cleaning of the glass plates of the windows36, with the slidable protection screen 28 there is associated for eachwindow 36 of the container 22 a rubber wiper blade (not visible in thedrawings) which with the movements of said screen slides along thecorresponding window, to maintain it clean.

[0047] From the aforegoing it is clear that the apparatus of theinvention is extremely advantageous, and in particular:

[0048] it enables the appropriate parameters of a railway line to bemeasured without any contact with the rails and without the need for anymechanical centering device,

[0049] by comparing the determined profile of a rail with itstheoretical profile it enables the degree of wear and vertical andhorizontal deformation to be ascertained,

[0050] it enables the rail geometry parameters to be measured,

[0051] it is insensitive to elastic deformation and oscillation of therailway carriage on which it is mounted, and hence effects readings freeof errors.

1. A laser apparatus for monitoring the rails of a railway or tramwayline, comprising for each rail (6) a measuring unit (4,8), provided withtriangulation reading devices using a laminar laser beam (2) generatedby a laser source (4) and directed towards the rail to be monitored, anda video camera (8) positioned at a certain angle to the laser beam (2),and further comprising a process unit for processing the signaltransmitted by said measurement units, said measurement and processorunits being mounted on a railway or tramway carriage made to advancealong said railway or tramway line, characterised in that: saidmeasurement unit comprises at least two triangulation reading devicespositioned aligned along the axis of the respective rail (6) andfocussed on the top of the rail head, and said processor unit comprisessoftware means able to calculate the derivative of the differentialmeasurement obtained from each of said at least two triangulationreading devices and hence to determine the undulatory wear of the rail.2. A laser apparatus as claimed in claim 1 characterised in that eachmeasurement unit further comprises a profile reading device, consistingof at least a triangulation device operating at least on the inner partof the respective rail.
 3. A laser apparatus as claimed in claim 2characterised in that it comprises a central measuring unit (10), inwhich said triangulation reading devices are located, and a pair of endmeasurement units (20,30) positioned upstream and downstream of saidcentral measurement unit (10) and each comprising at least one profilereading device of the same type as provided in said central unit (10),to determine together with this latter the track geometry, by processingthe signals generated by said profile reading device.
 4. An apparatus asclaimed in claim 3, characterised by comprising laser signal generators(34) located on the central measurement unit (10) and laser signalsensors (16) located on said end measurement units (20, 30) andoperationally associated with said laser signal generators (34) tomeasure the elastic deformations of the railway or tramway carriage andautomatically compensate the resultant measurement errors.
 5. Anapparatus as claimed in one or more of claims 1 to 4, characterised inthat each measurement unit (10, 20, 30) consists of a container (22) forthe various laser reading devices, which is applicable to the railway ortramway carriage and is provided in its base, which faces the rails (6),with windows (36) associated with the laser sources (4, 14, 24, 34) andwith the video cameras (8, 18, 28).
 6. An apparatus as claimed in claim5, characterised in that with that wall of the container (22) whichcomprises the windows (36) there is associated a screen (26) which isprovided with apertures positioned to coincide with said windows (36)and is slidable between two end positions, in one of which saidapertures face said windows.
 7. An apparatus as claimed in claim 6,characterised in that the screen (26) is provided with wiper bladesassociated with the various windows (36) of the container and slidablealong their glass as result of the movement of said screen.